解:(1)原式=6xy﹣3[3y2﹣x2+2xy+],
=6xy﹣9y2+3x2﹣6xy﹣3
=3x2﹣9y2﹣3;
当x=﹣2,y=﹣时,
原式=3×4﹣9×﹣3=8;
(2)原式=2x2﹣6x﹣4+4﹣4x﹣4x2
=﹣2x2﹣10x,
当x=5时,
原式=﹣2×25﹣10×5=﹣100;
(3)原式=2a2b+2ab2﹣2a2b+2﹣2ab2﹣2=0,
故当a=﹣2,b=2时,原式=0;
(4)原式=﹣x2+x﹣2﹣x+1=﹣x2﹣1,
当x=时,原式=﹣﹣1=﹣1.
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